1. Field of the Invention
The present invention relates to a method of forming aluminum metallized films and protective filmsxe2x80x94such as silicone plasma polymerized films for protecting the aluminum metallized filmsxe2x80x94on synthetic-resin base materials through lined up processing stages.
More specifically, the invention relates to a method of forming aluminum metallized films and silicone protective films through the steps of housing and lining up, in a predetermined case, a plurality of synthetic-resin base materials for use in various reflectorsxe2x80x94such as reflective mirrors for use in vehicular lamps such as automobiles, two-wheeled automobiles and the like, particularly synthetic-resin base materials of reflectors to be mounted in discharge headlampsxe2x80x94and passing the case successively through an aluminum metallizing chamber and a silicone protective film forming chamber. The invention also relates to a reflector formed by the above-described method.
2. Description of the Related Art
In the lamp chamber of a vehicular lampxe2x80x94such as a headlamp to be mounted in an automobile, a two-wheeled automobile or the likexe2x80x94a reflector, (such as a reflective mirror) For reflecting light emitted from a light source (such as an electric bulb) to convert the light to what is emitted outside, is disposed in such a manner as to embrace the light source.
The reflector, in a substantially cup (parabolic) form, has an opening oriented to a front lens. There flector is formed with an aluminum metallized film functioning as a reflective surface on the surface layer of synthetic-resin base material mainly made of BMC (Bulk Molding Compound). Further, a protective film, for preventing deterioration of the aluminum metallized film, is formed on the surface layer of the synthetic-resin base material.
In view of environmental problems resulting from the spillage of organic solvents and attempts to reduce raw material cost, a method of forming a silicone polymerized film on each of the base materials is increasingly employed. The method uses a plasma sourcexe2x80x94by way of a high-frequency induction discharge, a glow discharge, or the likexe2x80x94in place of a technique of forming a protective film by coating, in order to reduce a steamy silicone oil to plasma.
However, such a method still presents the following technical problem, namely, that aluminum metallized films and plasma polymerized films are formed on both sides of synthetic-resin base materials.
First, when a xe2x80x98rotating and revolving metallizing systemxe2x80x99 is used, the steps of forming aluminum metallized films and plasma polymerized films will have to be followed separately. Separate steps are necessary because the xe2x80x98rotating and metallizing systemxe2x80x99 is specifically designed for forming metallized films by disposing a plurality of base materials so as to respectively face aluminum metallizing sources arranged along the central axis of a large cylindrical chamber, and then for causing the base materials to rotate on the aluminum metallizing sources. For this reason, these processing stepsxe2x80x94for forming metallized films and for forming polymerized protective filmsxe2x80x94are multi-staged and necessitate a step of conveying the base materials when one step is shifted to the other. Moreover, as the rotating and revolving system is equipped with a rotating mechanism, as an aluminum metallizing system, it is complicated in construction.
There is also known an antenna-type plasma polymerizing system for forming aluminum metallized films and plasma polymerized films in one large chamber. In the antenna-type system, plasma is generated by way of a high-frequency oscillation antenna within a chamber so as to polymerize monomers introduced into the chamber. With the use of such a system, it is possible to form aluminum metallized films and plasma polymerized films through a series of operations.
However, the drawback of the antenna-type system is that: it is a batch production system wherein a large number of predetermined base materials are disposed in a chamber and, after a predetermined time (about 40 minutes) for forming metallized films and plasma polymerized films elapses, all of the base materials are taken out of the chamber; a lead time, necessary for disposing the base materials in the chamber is long; and when any poor quality is found in the relevant lot, many of the base materials will also be found poor in quality.
An additional problem is that the formation of plasma polymerized films by the antenna-type system results in low plasma density in general, and causes not only slow film formation but also uneven film distribution.
The aluminum metallized film sometimes is utilized as a noise shield (electromagnetic shield) when formed on the back surface of a reflector that is used in a discharge headlamp. The problem in this case is, technically, that when a plasma polymerized film (silicone polymerized film) is also formed on the aluminum metallized film on the back surface of the reflector, as in the antenna-type system, the aluminum metallized film may not be grounded.
An object of the present invention is to provide a film forming technique so devised that aluminum metallized films and plasma polymerized films are formed through a series of lined-up steps, and so that a protective film (silicone polymerized film) is not formed on the back surface of any reflector base material, whereby a protective film may easily be formed even on a reflector to be utilized in a discharge headlamp.
In order to accomplish the above and other objects, the following aspects of the invention are adopted.
In a first aspect of the invention, a plurality of synthetic-resin base materials are placed at predetermined intervals in a framexe2x80x94like case via jigs. Further, an aluminum metallized film is formed on both sides of each one of the synthetic-resin base materials, and a protective film is formed on the upper layer of the aluminum metallized film, by moving the case by a conveyer, for example, successively through an aluminum metallizing chamber and a plasma polymerized film forming chamber.
With this arrangement, one only needs to install each synthetic-resin base material onto an upwardly-open case. Therefore, the work required to set the base materials can be simplified, and the lead time can also be shortened.
The stepsxe2x80x94of forming metallized aluminum and plasma polymerized, filmsxe2x80x94that have heretofore been separately followed can now be performed in series, whereby the work of conveying synthetic-resin base materials from the aluminum metallizing stage to the plasma polymerized film forming stage can be omitted, which further shortens the lead time.
Further, because the films are formed as the case is passed laterally through an aluminum metallizing chamber and a plasma polymerized film forming chamber, a complicated mechanism for rotating base materials in any metallized-film forming unit can be dispensed with.
A preliminary vacuum chamber, for forming a low vacuum condition in preparation for the metallizing step, is provided in front of the aluminum metallizing chamber, and is kept in a high vacuum condition. Another preliminary vacuum chamber, for returning the high vacuum condition to a low vacuum condition, is provided in the rear of the plasma polymerized film forming chamber.
Moreover, because it is necessary to secure surface smoothness of each base material before the aluminum metallizing step, the surface smoothness of the base material must be secured by providing an undercoat to the synthetic-resin base material, or otherwise devising a special base material.
According to the invention, installation of the case is simplified, even when the undercoat layer is provided to each synthetic-resin base material before the aluminum metallizing step. That is, while one holds the back side (rear top portion side) of the synthetic-resin base material without touching the undercoat layer, it can be moved from the undercoat process to the case in which it will be metallized.
Incidentally, the invention is widely applicable to, for example, formation of frame-like rims, films for automotive lamp forming members, and the like, that have aluminum metallized films on their surfaces.
In a second aspect of the invention, the synthetic-resin base materials, which have sequentially been formed with aluminum metallized films and plasma polymerized films, are taken out of the case, and the empty case is conveyed to the side of the aluminum metallizing chamber whereby it can be used repeatedly.
This is convenient because the case is usable for housing, without manually moving, the synthetic-resin base materials. Although the shape and size of such a case are not restrictive, it is preferred to line up 8 or 10 synthetic-resin base materials at predetermined intervals in one case. Such case size is beneficial in consideration of the formation of aluminum metallized films facing the back surface of the respective base materials, and in consideration of the time required to set the base materials in the case.
In a third aspect of the invention, the line-type film-forming method is applied to substantially cup-shaped reflector base materials that are to be mounted in a vehicular lamp.
The cup-shaped reflector base materials include an extension reflector, for concealing the gaps between the lamp body and the reflector, and between the lamp body and the projection lens. The cup-shaped reflector base materials also include a reflector for use as are flective mirror that reflects light emitted from a bulb.
In a fourth aspect of the invention, the reflector base materials are disposed so that they are laid face down, i.e., each of its rear top portions is directed upward. The aluminum metallized film is formed on both the front surface and the back surface of each reflector base material by blowing aluminum, from below the reflector base materials, in the aluminum metallizing chamber. Further, the plasma polymerized film is formed, in the plasmapolymerized film forming chamber, on only the front surface of each reflector base material.
More specifically, pluralities of aluminum metallizing and plasma sources are arranged in the lower regions of the respective aluminum metallizing, and the plasma polymerized film forming, chambers. With respect to aluminum, a metallized film is formed on both the front surface and back surface of each reflector base material by utilizing the property of the aluminum moving around toward the back surface of the base material. In contrast, the silicone is restricted in its diffusing area, so that the silicone polymerized film is formed only on the front surface (i.e., the face directed downward) of each reflector base material.
The reflector base materials are preferably lined up at predetermined intervals to ensure that the aluminum metallized film is formed on the back surface of each reflector base material. Incidentally, by the xe2x80x98openingxe2x80x99, it is meant an opening oriented toward the front lens when the reflector is disposed in the lamp chamber; it is not the bulb mounting hole formed in the rear top portion of the reflector base material.
Because the aluminum metallized film is formed on the back surface of the reflector for the discharge headlamp, when it is formed by the line-type film-forming method according to the fourth aspect of the invention, it is ensured that an electromagnetic shielding function can be achieved. That is, since the aluminum metallized film is exposed to the back surface of the reflector, without being covered by a protective film, the back surface of the reflector can easily be grounded.
As set forth above, the invention contributes technology to improving the quality of reflectors for use vehicular lamps. In addition, the invention contributes to improvements not only in workability of forming aluminum metallized films and silicone polymerized films, but also to improvements in productivity thereof.